1. Field of the Invention
This invention relates to improved corrugated steel decking for use in construction of buildings and more particularly to cellular steel flooring which is employed for electrical distribution systems or air distribution systems in a building.
2. Description of the Prior Art
Corrugated steel decking has been employed as a construction material in highrise buildings for many years. The corrugated steel decking is secured to a building framework and is covered with wet concrete which is allowed to harden. The hardened concrete becomes the walking surface for the floors of the resulting buldings. Usually the corrugated steel decking is equipped with indentations or embossments which improve the mechanical bond between the decking and the hardened concrete whereby the concrete and decking cooperate compositely to improve the load-carrying capability of the resulting building floor when compared to the load-carrying ability of the decking itself or of the concrete itself. The strength of the corrugated steel decking must be considered at two different stages of its useful life. Firstly, during the construction stages of the building when the corrugated steel decking is secured to the building framework and before concrete has hardened in engagement with the decking, the corrugated steel decking must have sufficient strength to support its own weight, the weight of typical constructon traffic (workmen, construction tools, concrete buggies). Also, after the concrete has been poured, the corrugated steel decking must sustain the parasitic load of the wet concrete which makes no contribution to the load-carrying capability of the resulting floor until it has become hardened. This first strength consideration is known as the wet strength of the steel decking. Secondly, the corrugated steel decking must cooperate compositely with the hardened concrete whereby the load-carrying capability of the composite flooring exceeds the load-carrying capability of the corrugatd steel decking alone. This second strength consideration is known as the composite strength of the steel decking.
Cellular corrugated steel decking has been employed for more than 40 years to function not only as a floor-forming member of a building but also as an electrical distribution system or an air distribution system for the resulting building. The cellular floor typically has been manufactured by combining a flat steel sheet with a corrugated steel sheet whereby individual enclosed lengthwise cells are formed between each corrugation of the corrugated steel decking and the flat sheet. Many permutations of flat sheets and corrugated steel decking are known in the art. Permutations of two corrugated steel decking sections secured together in alignment also have been employed. There are cellular steel decking installations which employ conventional cellular steel decking along with a separate cover plate which encloses a valley between adjacent cells to provide supplemental electrical distribution capacity for the resulting steel flooring, e.g., Fork, U.S. Pat. No. 3,592,956.
The cellular steel flooring of the prior art predominantly employed a flat bottom steel sheet and a corrugated upper steel sheet to define wire-carrying passageways or cells. The principal shortcoming of this construction is that the crest surfaces of the corrugated decking or the sloping web surfaces of the corrugated decking must be penetrated in order to provide wiring access into or out of the individual cells. Such penetrations of the corrugated decking reduce the load-carrying ability of the decking, primarily the wet strength of the decking.
A further shortcoming of prior art cellular steel flooring products is that the access openings or penetrations in the crest surfaces are relatively small and hence present difficulties to workmen who are attempting to introduce wiring into the cells or to extract wiring from the cells.
A still further shortcoming of the cellular steel flooring installations arises from the requirement that the undersurfaces of such decking be covered with an appropriate fireproofing substance. The flat bottom surface of conventional cellular steel decking resists reliable adhesion of typical fireproofing materials. The fireproofing materials adhere more reliably to corrugated surfaces rather than to wide horizontal flat surfaces.
A still further shortcoming of conventional cellular steel decking is the expense of shipment resulting from the fact that cellular steel decking cannot be nested for transportation but instead must be stacked section-by-section with a significant volume of included air space.
When cellular steel decking has been employed for distributing air throughout a building, continuous welding techniques were employed to assure that the resulting cells were airtight. The expense of such continuous welding assemblies has been a significant factor in the lack of commercial success of cellular steel decking for air distribution.